Cant update genre of video anymore

I wrote a python script that adds missing custom genres to videos, after an update of jellyfin my script stopped working and I'm only getting Error 500 Messages.

My code (simplified):

```
from jellyfin_apiclient_python import JellyfinClient

client = JellyfinClient()

client.config.app('your_brilliant_app', '0.0.1', 'machine_name', 'unique_id')
client.config.auth('http://10.1.1.148:8096',
'here_was_my_token',
'here_was_my_api_key',
False)
client.auth.connect()

new_genres = {"Genres": ["Test"]}
client.jellyfin.update_item('caaddfbe1a9d6c8b5a949922f92617b0', new_genres)
```

Console Output:

```
500 Server Error: Internal Server Error for url: http://10.1.1.148:8096/Items/caaddfbe1a9d6c8b5a949922f92617b0
--[ 500 response ] 500 Server Error: Internal Server Error for url: http://10.1.1.148:8096/Items/caaddfbe1a9d6c8b5a949922f92617b0
```

Start with the JellyfinClient setup and the update_item call shown in the issue, then reproduce the 500 response against the /Items/{id} endpoint. Compare the client request with the endpoint behavior after the Jellyfin update; done means updating the video's Genres succeeds without an internal-server error.

Written by the indexing model from the issue text.